Molecular recognition based on membrane potential changes induced by host-guest complexation with inorganic and organic guests

Guest-induced changes in membrane potentials are one of the representative modes of electrochemical signal transduction by molecular recognition at the interface of an organic membrane and an aqueous solution. Recent approaches based on synthetic hosts capable of effecting membrane potential changes by host-guest complexation with inorganic and organic guests are described. Although the studies in this area have mainly been aimed at inorganic cations as the target guests, recent approaches for recognition of inorganic anions and further organic guests are also documented. Highly selective changes in membrane potentials can be achieved for inorganic cations by sophisticated design of crown ethers and related compounds. Hosts with complementary charge(s) or multiple hydrogen bonding sites are effective for the recognition of inorganic anions and also of the polar moieties of organic ions. On the other hand, the recognition of nonpolar moieties of organic guests can be achieved by inclusion into well-defined cavities of host molecules. Quaternary onium and protonated amine salts are recently found to be capable of effecting membrane potential changes by complexation with neutral phenolic guests.